1. Field of the Invention
The present invention relates to a liquid injection recording apparatus, and, more particularly, it relates to a liquid injection recording apparatus in which the recording is effected by liquid drops discharged from discharge ports.
2. Related Background Art
As a conventional liquid injection recording apparatus of this kind, a recording apparatus wherein minute liquid drops are discharged by creating pressure change in liquid passages due to the deformation of piezo-electric elements, and a recording apparatus wherein a pair of electrodes are further provided for deflecting liquid drops when discharged, has been already known. Further, various recording systems such as a recording apparatus wherein exothermic elements are arranged in liquid passages and liquid drops are discharged from discharge ports by bubbles generated by suddenly heating such exothermic elements have been proposed.
Among these conventional recording apparatuses, the last mentioned recording system, i.e., the system that utilizes thermal energy to discharge the liquid drops is particularly effective in that it is easy to arrange the discharge ports with high density and it is possible to record at a high speed. Further, as recording heads applicable to such a recording apparatus, a recording head of serial scanning type and a recording head of full-multi (full-line) type such that the discharge ports are arranged in correspondence to a width of the record are already known. Among them, the recording head of full-multi type is apparently effective in the high speed recording operation.
However, in the recording head used with the above-mentioned recording apparatus that utilizes thermal energy, when a high density recording operation such as a solid recording operation, particularly a high speed recording operation by high-frequency drive is carried out, there arise problems that the temperature of the recording head is excessively increased due to excessive heat which is not utilized to record (i.e., to form the liquid drops), thus changing the viscosity of the recording liquid or generating dissolved bubbles in the recording liquid, and that the formation of desired bubbles cannot be obtained when the temperature of the recording head is increased more than a certain value T1. The excessive temperature increase in the recording head often makes difficult the formation of the proper or normal liquid drops and/or changes the diameter of a dot, thus deteriorating the quality of the record. Further, since the bubbles (dissolved bubbles) created by releasing dissolved gas in the recording liquid do not vanish immediately, they remain in the recording head for a long time. As a result, they absorb the sudden pressure change required for forming the liquid drops due to the formation of bubbles, thus often resulting to non-discharge of the liquid drops.
For these reasons, in the conventional recording apparatus, in order to cope with the above problems and disadvantages, when the temperature of the recording head reached a predetermined value T2 set lower than the temperature T1, the recording operation was temporarily stopped until the recording head was cooled to a certain temperature, and thereafter the recording operation was started again. Particularly, such temperature increase should cause a remarkable problem, since when the recording head is of full-multi type including the recording system for forming the liquid drops by utilizing thermal energy, the number of the exothermic elements (heating elements) may be a few thousand. However, if the recording operations are temporarily stopped, the advantage of high speed recording is lost, even when the recording system for permitting the high speed recording operation is used and the ability of such a recording system cannot be effectively utilized.